1. Field of the Invention
The present invention relates to a photomask mounting/housing device and a resist inspection method and resist inspection apparatus using the same and more particularly to the photomask mounting/housing device configured so that a photomask can be easily separated from a translucent protective member and the resist inspection method using the photomask mounting/housing device and the resist inspection apparatus having the photomask mounting/housing device.
2. Description of the Related Art
Conventionally, a photomask (reticle) is used to manufacture semiconductor integrated circuits. Before the photomask is used for manufacturing semiconductor integrated circuits, an inspection is performed to check whether a resist formed on a substrate of a photomask has an expected and predetermined pattern. Various types of technologies have been developed for the inspection of resists. Examples of these technologies are described below.
One example of the related resist inspection apparatus is shown in FIG. 4. As shown in FIG. 4, in the related resist inspection apparatus, light 31 for resist inspection is applied from one side of a reticle 2 and a pattern image is formed based on reflected light fed through an optical element such as a lens 30 and a desired inspection is performed using the obtained pattern image itself or by comparison between the obtained pattern image and a pattern image designed in advance. This example is disclosed in Patent Reference 1 (Japanese Patent Application Laid-open No. Hei06-020934).
Also, in another example of a related resist inspection apparatus whose rough configurations are the same as those shown in FIG. 4, the resist is inspected while air purging is performed on optical elements in the same way as shown in FIG. 4. This example is disclosed, for example, in Patent Reference 2 (Japanese Patent Application Laid-open No. 2006-245400).
Also, in still another example of a related resist inspection apparatus, as shown in FIG. 3, as a photomask to be used in the resist inspection apparatus, a pellicle 3 is coupled to a reticle 2. This example is disclosed in Patent Reference 3 (Japanese Patent Application Laid-open No. 2003-315983).
Furthermore, in still another example of a related resist inspection apparatus, a pellicle frame attached to a pattern surface of a photomask is divided, by pin-coupling, into two portions, an upper frame and a lower frame. This example is disclosed in Patent Reference 4 (Japanese Patent Application Laid-open No. Hei05-216214).
However, the above related technologies have the following problems. That is, in the case of the related resist apparatus disclosed in the Patent Reference 1, when the light 31 for inspection is applied to the resist 7 on the reticle 2, gas 20 is released from the resist 7, which causes the gas 20 to remain, as an adherent 21, on a surface of an optical element such as the lens 30 (see FIG. 6). There is a technological problem that, if the residual adherent 21 occurs at every tine of the inspection, the performance of the optical element of the lens 30 is degraded and finally the inspection becomes impossible. A countermeasure against the degradation of the lens performance is to wipe the adherent 21 off the lens 30, however, it is impossible to fully restore the performance of the lens 30 only by the wiping method and, therefore, unless the lens 30 is replaced, the continuation of the inspection is made impossible. Even in the case where the inspection is to be continued by replacing the lens 30, the lens 30 is expensive and its delivery time is long, thus causing costs to mount and much time to be taken for the repairing process.
The residual adherent 21 caused by the gas presents further problems. That is, if the inspection is performed on another reticle 2b in a state where the adherent 21 is being left, as shown in FIG. 7, the residual adherent 21 causes a difference between a pattern image to be obtained from the inspection and a pattern image designed in advance and, as a result, the difference in pattern is extracted, as a defect, together with an actual defect that may occur in the resist 7b by the image comparing device in the resist inspection apparatus.
If the above information only is used for the comparison, it is made impossible to differentiate between the defect caused by the residual adherent 21 and the actual defect of the resist 7b. In order to achieve the exact differentiation, the further processes of inspection and/or checking are required which include the method by the re-inspection with the reticle 2b rotated horizontally by 90, 180, or 270 degrees, etching of the reticle 2b, detailed checking of the lens 30, or the like.
Out of the above differentiation methods, the re-inspection method by the rotation of the reticle 2b presents a further problem, that is, during the re-inspection process, the adherent 21 is accumulated more, which possibly makes it more difficult to differentiate between the defect caused by the residual adherent 21 and the actual defect of the resist 7b. Also, in the case of the differentiation method by etching the reticle 2b for checking, if an actual defect is found in the resist 7b, the use of the reticle 2b becomes impossible. Furthermore, the method by detailed checking of the lens 30 is practically impossible due to its difficulty and time required for the checking process.
Various countermeasures against the degradation of performance of optical elements such as the lens 30 are available, however, a peculiar technological problem still arises in each of the countermeasures. Therefore, the technological problem related to the degradation of performance of optical elements such as the lens 30 caused by gas remains unsolved. The technological problem related to the degradation of performance of optical elements is partially solved by the technology disclosed in the Patent Reference 2.
However, there is the following technological problem in the above technology using the air purge. In the technology disclosed in the Patent Reference 2, the air purging is performed on the optical element to avoid the direct contact between the gas 20 and lens 30. However, unless the purging air is rectified smoothly to purge the lens 30, the fluctuation of inspection light 31 occurs, as a result, making it difficult to obtain the uniformity of the light 31 which causes unevenness in image to show up and makes it impossible to perform the inspection itself. Furthermore, due to the attachment of the air purging component, difficulties exist in the maintenance of the apparatus.
The technological problem arises in the method disclosed in the Patent Reference 3. That is, if the resist 7 on a photomask is to be inspected by using the method, when the resist 7 is re-formed or etched after the inspection, it is necessary to take out the pellicle 3 or the pellicle 3 together with the pellicle frame 8 from the reticle 2 and, therefore, during the process of the removal, the reticle 2 may be contaminated or damaged.
The Patent Reference 4 discloses the configuration in which a photomask is housed between the two pellicle frames being pin-coupled to each other, thus requiring an upper frame and a lower frame. However, no configuration is suggested in which a photomask is housed in a pellicle frame to which a pellicle is attached in an stretched manner.